S&P text on outlook:
The negative outlook on our rating on the U.S. sovereign signals that we believe there is at least a one-in-three likelihood that we could lower our long-term rating on the U.S. within two years. The outlook reflects our view of the increased risk that the political negotiations over when and how to address both the medium- and long-term fiscal challenges will persist until at least after national elections in 2012. Some compromise that achieves agreement on a comprehensive budgetary consolidation program--containing deficit reduction measures in amounts near those recently proposed, and combined with meaningful steps toward implementation by 2013--is our baseline assumption and could lead us to revise the outlook back to stable. Alternatively, the lack of such an agreement or a significant further fiscal deterioration for any reason could lead us to lower the rating.